Process and device for drawing truncated-cone shaped bodies and the like



Dec. 16. 1969 D. GROPPINI 3,483,728

PROCESS AND DEVICE FOR DRAWING TRUNCATED-CGNE SHAPED BODIES AND THE LIKE Filed Jan. '24, 1967 4 Sheets-Sheet l ATTORNEY Dec. 16. 1969 D. GROPPINI 3,483,728

PROCESS AND DEVICE FOR DRAWING TRUNCATED-CONE SHAPED BODIES AND THE LIKE Filed Jan. 24, 1967 4 Sheets-Sheet 2 FIG. 2

Dec. 16. 1969 D. GROPPINI 3,483,728

PROCESS AND DEVICE FOR DRAWING TRUNCATED-GONE Filed Jan. 24, 1967 r U PO 2 Q 1 LL. PO 2 u.

SHAPED BODIES AND THE LIKE 4 Sheets-Sheet 3 u m F3 0 C E 2 u.

Dec. 16. 1969 D. GROPF'INI 3,433,723

PROCESS AND DEVICE FOR DRAWING TRUN ED-CONE SHAPED BODIES AND THE LIK Filed Jan. 24, 1967 4 Sheets-Sheet 4 FIG. 4

FlG.5

US. Cl. 722-250 4 Claims ABSCT OF THE DISCLOSURE Elongated truncatedcone shaped bodies are drawn in a drawing stand wherein automatic means are employed to retrun the drawing rolls to their starting positions after each drawing pass and wherein the rolls of the stand are profiled for a part of their groove length with a decreasing radius and for the remaining groove length with a minimum constant radius.

There are processes and devices known in the art, to produce, by means of drawing or rolling, truncated-cone shaped bodies or the like. For example, to make tubular, truncated-cone shaped bodies, one starts from a cylindrical tube which is first heated to a convenient temperature and then drawn through one or several roll-stands the opening of which is progresively variable.

In particular, when using one single roll-stand, the said stand should embody two or several rolls to define an opening the section of which is progressively and continuously variable during the drawing operation by means of the rotational motion of the said rolls which are externally driven, to obtain the desired conicity of the drawn piece.

To obtain an opening with circular cross-section and with a continuous profile, in order to obtain perfectly circular reduced sections and, at the same time, to prevent the material from being nipped between the rolls during the execution of substantial reductions, the use of stands fitted with two or several rolls has been proposed, the axis of the said rolls being coplanar, whereby the said rolls co-operate with each other, on at least one part of the drawing section, by means of teeth or the like which penetrate in each other, in order to form, also at a distance from the plane of the rotating axles, a substantially continuous profile.

Devices of the above mentioned type have already been described in known patents, for instance, in German Patent 153,138 and in United States Patent 3,044,331. However, the said device shows, by itself, in practice, some technological limits since it is impossible to obtain, by means of one single drawing stroke, the reduction of the diameter (i.e. the dilference between the bottom and the top diameter of the truncated-cone shaped body) beyond a certain limit, the said limit being due to the resistance to deformation of the metal to draw. This limit is generally insufiicient to satisfy the present demand of the market, which requires truncated-cone shaped bodies of considerable length which at their small end must, consequently, undergo a heavy reduction in diameter (to reduce the weight of the said bodies as much 'as possible and at the same time to maintain the highest possible resistance to mechanical stress).

Now, the present invention concerns a device which allow to obtain, in a practical and economical way, truncated-cone shaped bodies, the reduction of the diameter of the said bodies being defined by the profile of the drawing rolls and the length of which can be practically nited States Patent 0 Lil unlimited, i.e. in practice limited only by the length of the drawing bench. It is understood that the invention extends also to the product which is obtained by means of the said device.

The invention is substantially characterized in that the drawing from the cylindrical body to the finished truncated-cone shaped piece is performed in the same rollstand, by means of several passes which are performed in rapid succession, over progressively increasing lengths, maintaining the same conicity for each stroke and hence, for each length. v

The said devices are substantially characterized by:

A hydraulic piston with constant presusre, connected to the rolls of the stand, the said piston moving during the drawing pass, overcoming the pressure of the fluid at the expenses of the roll driving motor, whereby the said piston, at the end of the drawing stroke-after disengagement of a joint connecting the driving motor and the rolls-moves quickly in the opposite direction, thanks to the pressure of the fluid, causing the quick and automatic return of the rolls to the starting position, the said rolls being thus ready for the next successive pass; hence the said return is not performed in synchronism with the return of the drawing carriage, but with a considerable advance of time over the same;

a second hydrauiic piston, also under constant pressure but so dimensioned as to prevail over the preceding piston to which it is connected, the said piston being designed to damp the impact due to the inertia force of the masses in motion at the end of the return stroke of the rolls; and being mainly designed to return the rolls to their exact starting position which is preset according to the diameter of the cylindrical body to be drawn;

adjustable limit switches on the drawing bench, the number of which is equal to the number of strokes to be performed, said limit switches being set according to the length to be drawn at each pass and in such a manner as to cause the drawing operation to start automatically exactly at the pre-established point, so as to draw, over the desired length, at each single pass,

structural improvements applied to the rolls of the drawing stand to provide improved technical results and to save on production costs.

With the devices of the invention it is possible to obtain, in practice, with more than one operation but in one single heat, reductions in diameter as great as 50%, over lengths, limited only by the length of the drawing bench. The said value is sufiicient to meet the market requirements in almost any case. It is also possible to shape the drawing rolls so as to obtain reductions in the diameter up to 75% which can be obtained in two heats without changing the rolls and in a sufficiently quick and economical way.

The invention will be more specifically described hereinafter with reference to the accompanying schematic drawings, the specification and drawings being given only as an indicative example, without limiting the invention.

FIGURE 1 is a plan view of the general arrangement of a drawing plant for the production of truncated-cone shaped bodies;

FIGURE 2 is a detail, seen from X, of FIGURE 1;

FIGURES 3a through 3 show the successive stages of the processing cycles of a truncated-cone shaped body;

FIGURE 4 shows, in front elevation, a drawing stand with three rolls, wherein the drawing opening is set to the smallest diameter;

FIGURE 5 is a cross section along line 55 of FIG- URE 4; and

FIGURE 6 is a section on line 66 of FIGURE 5.

With reference to FIGURES 1 and 2, 1 indicates the heating furnace of the tubes to be drawn and 2 the drawing bench which is co-axial with the furnace discharging line 6 and with the drawing roll-stand 3 situated in proximity of furnace 1. The drawing carriage 4 which supports the nipping-jaws 5 of the pointed end of the tube 7 to be drawn is driven, through a chain 8, and a gear box 9 by a motor 11. The rotation of the coneshaped drawing rolls housed in the roll-stand 3, is obtained by means of the shafts 12 and 13 (connected to one another by means of a joint 14), a gear box 15, a coupling 16, a second gear box 17 and a motor 18.

During the drawing operation, the motor 18 is coupled to the main motor 11 at a constant ratio which is preset according to the drawing rolls profile, to obtain the desired conicity of the work piece. The coupling device, which can be of any known type, either electrical or mechanical, is not shown in the figure.

The ratio between the speeds of the motors 11 and 18 can be varied, within certain limits, by acting on the coupling system, in such a manner as to very the conicity of the piece to be drawn through still utilizing the same rolls.

19 shows a chain wheel (star) FIGS. 1 and 2 mounted on the slow shaft 13 of the gear box 15, which serves to obtain the quick return of the rolls to the initial position, at the end of a drawing stroke.

FIGURE 2 shows, in detail, the device for the quick return of the rolls. Wheel 19 is linked, by means of chain 20, to a second wheel 21 fitted below the first mentioned wheel. Wheel 21 is mounted at the end of the piston shaft of a single throw piston 22 which slides in a fixed cylinder 23, the chamber 24 of said cylinder being constantly under the pressure of a pressurized fluid (water or oil) that reaches cylinder 23 through duct 24'. One end of chain 20 is linked to the shaft of a second single throw piston 25, that slides in a fixed cylinder 26, the chamber 27 of which is under a constant pressure fed through conduit 27'. The other end of chain 20 is linked to cylinder 26 and is therefore fixed.

Piston 25, in its position at the end of the downward stroke, sets the starting position for the rolls of stand 3 position in which the diameter of the drawing opening, as required by the work piece to be drawn, reaches its maximum extension).

The said position can be set according to the different diameters of the work piece, by suitable angular displacement of shaft 12 shown in FIG. 1 (said shaft providing the rotational motion of the rolls) with respect to shaft 13. During the drawing phase (in which carriage 4 moves in the direction A as shown in FIGURE 1), coupling 16 is engaged to connect the gear boxes and 17 to each other, said gear boxes taking their motion from motor 18, and said motor driving the shaft of stand 3 and therefore causing the rotation of the rolls. Accordingly, wheel 19 rotates in direction C, as shown in FIGURE 2, to pull chain 20, thus causing wheel 21 and piston 22 to move upwards and, consequently, to evacuate the fluid contained in chamber 24 through the conduit 24'.

The chain length 20, as pulled back by wheel 19, rests free in the area above the shaft of piston 25, whilst the latter is in its downward end position. After accomplishment of the drawing stroke that is, when the end of the work piece 7 protrudes from roll-stand 3, carriage 4 comes to a stand-still, coupling 16 is automatically disconnected by means of a suitable drive member (not shown in the figure). Since the torque in direction C comes to zero, the fluid pressure in chamber 24 prevails, and urges piston 22 and Wheel 21 downwards, said parts providing, in turn, to pull chain 20, causing the quick reverse rotation of wheel 19, in direction D in FIGURE 2 and, consequently, a return, to starting position, of the rolls of stand 3. When the rotation of wheel 19, again causes pulling of chain length which as previously mentioned, rests loose in the area above the shaft of piston 25, piston itself performs an upward motion by eifect of the pull, as a result of which the fluid tained in chamber 27 damps the impact caused by the inertial force of the masses in motion, and comes to a quick stand-still. Since piston 25 is so sized as to prevail over the action produced by piston 22, the first mentioned piston thereafter returns to its downward end position, thus setting the exact starting position of the roll of stand 3.

At this stage, carriage 4 starts on its return stroke (obtained by reversing the motion of main motor 11), in the direction shown by B in FIGURE 1, to again shift work piece 7 across stand 3, back to starting position and ready for the next successive stroke.

Concluding, the return of the rolls to their initial position takes place automatically, by disengagement of the same from the drive which is used during the drawing phase and utilizing a different drive, the last mentioned drive consisting essentially of a hydraulic cylinder-andpiston assembly allowing for quickest return, whereby said backward motion is no longer performed in synchronism with the backward motion of the drawing carriage, but with a considerable time advance over the said motion. The stop of the rotating rolls in the exact position desired, is obtained through a second hydraulic cylinder-piston assembly which acts, at the same time, as a shock-absorber of the impact caused by the inertial force of the moving masses.

FIGURES 3a through 3; show the successive steps of the drawing of a truncated-cone shaped body, starting from a cylindrical work piece, and obtained by three successive drawing operations, over progressively increasing lengths (involving the full length of the work piece, at the last drawing stroke), by maintaining the same conicity for each stroke and hence for each length.

The drawing stand is shown schematically with one single roll 30, sectioned according to the medium plane which is perpendicular to the axis of rotation.

FIGURES 3a3c3e show the starting positions of the processing stage of the piece during the first, second and third drawing passes, respectively.

Prior to the single drawing operations, the drawing rolls are exactly in the same position, each time, so as to form a drawing opening, the diameter of which is identical with that of the cylindrical work piece (in practice, the opening diameter is slightly greater, to allow the easy passage of the work piece through the cage, both during the introduction and the return stage). The lengths L L L to be drawn at each stroke (said length being precalculated according to the maximum obtainable reduction of the diameter at each stroke), are pre-set on the drawing bench by means of adjustable limit-switches 31, 32 and 33, which consent automatic starting at the appropriate stage of the drawing operation (said limit-switches cause the engagement of coupling 16, shown in FIGURE 1, to start rotation of the drawing rolls in synchronism with the motion of the drawing bench). FIGURES 3!). 3d and 3 show the positions of the piece at the end or the first, second and third passes, respectively. FIGURE 5 is a detailed cross sectional view of the shape of a drawing roll, according to a medium plane, perpendicular to the axis of rotation.

The continuous line 34 shows the section of the groove bottom of a new roll, consisting of a groove length 34 with decreasing radius, R FIGURE 6 and of a groove length 34" having a minimum constant radius R" also shown in FIGURE 6.

It is possible to maintain the same, minimum groove radius of the new roll during the successive re-dressings of the groove at the expense of length 34", whilst yet maintaining the profile unaltered and gradually increasing the maximum radius of the groove. Thus, the length 34" makes it possible to utilize to a maximum extent the groove profile, whose minimum radius is identical to that of the new roll. Said utilization is possible up to exhaustion of length 34"; at this point profile 35 of the groove bottom is that shown by a dot-and-dash line in FIGURE 5 5. Said profile represents the utilization limit for the minimum drawing-diameter for which the roll has been designed.

Subsequently, the roll can still be utilized for greater drawing diameters, by re-dressing the groove and by progressively increasing also the minimum radius, until profile 36 (as shown with a dash line in FIGURE 5) is reached, and beyond which limit the roll is no longer utilizable.

FIGURE 5 also shows that the passage from minimum to maximum radius of the groove is not gradual, but has a sharp step (shown by 37 on profile 34 corresponding to the new roll).

The height of said step is set in relation to the last dressing of the roll. This affords a saving of material and, at the same time, a reduction of the time required to redress the groove as the re-dressings will be limited to the working portion of the groove itself.

As shown in FIGURE 4, two toothings of a same roll are ofiset, by half a pitch, with respect to each other. This arrangement, which is aimed at providing accurate engagement between the toothings of two adjacent rolls, would not be necessary in stands fitted with an even number of rolls and would be required for one roll only in stands fitted with an uneven number of rolls; however, it serves to render all of the rolls of one stand perfectly equal and interchangeable, with obvious practical and eco* nomical advantages.

It is understood that several modifications can be brought to the above described devices, without departing from the spirit of the present invention or from the scope of the appended claims.

I claim:

l. A device for drawing truncated-cone shaped bodies characterized by a drawing stand having drawing rolls, a first hydraulic piston under a substantially constant pressure connected to the rolls of the stand, a roll driving motor, means selectively coupling said motor to said rolls, said roll driving motor overcoming the constant pressure acting against said first hydraulic piston during the draw ing pass to drive said rolls in one direction, wherein said piston, at the end of the drawing pass, when said driving motor is uncoupled from said rolls, drives said rolls in a direction opposite to said one direction due to the fiuid pressure acting on said piston, causing the quick and auto matic return of the rolls to the starting position.

2. The invention defined in claim 1 characterized by a second, hydraulic piston under constant pressure, said second piston being so sized as to prevail over the first piston, said first and second pistons being connected to one another, the second piston being designed to damp the impact due to the inertial force of the masses in motion at the end of the return stroke of the rolls; said second piston also adapted to return the rolls just to a preset starting position.

3. Drawing rolls for a drawing bench for drawing truncated-cone shaped bodies characterized in that the draw ing rolls when new are profiled for a part of the groove length with a decreasing radius and for the remaining groove length with a minimum, constant radius, and a sharp step between the minimum and the maximum radii of the grooves on the rolls profile, said rolls further characterized in that the same minimum groove radius of the new roll is maintained during several dressings, whereby the profile is maintained unaltered and only the maximum groove radius is increased gradually.

4. The invention defined in claim 3 wherein each draw ing roll is provided with a pair of bevel gears, one on each side of the roll groove, which bevel gears connect together the rolls of the stand, said pair of bevel gears characterized in that the teeth at one end of each of the rolls are olfset by half a pitch with respect to the teeth of the other end.

References Cited UNITED STATES PATENTS 73,715 1/1868 Harding 72276 1,810,885 6/ 1931 Neuberth 7225O 1,871,743 8/1932 Sawyer 72276 2,597,623 5/1952 Dies et a1 72276 2,679,925 6/1954 McIlvried et a1. 72276 3,240,045 3/1966 Sellars et al 72276 3,252,314 5/1966 Winnail 7229O 3,274,816 9/1966 Held 72214 3,330,145 7/1967 Adolphi 72277 CHARLES W. LANHAM, Primary Examiner E. M. COMES, Assistant Examiner US. Cl. X.R. 72119, 214, 224 

